Abstract
BackgroundCoarse woody debris (CWD) is very important for forest ecosystems, particularly for biodiversity and carbon storage. Its relevance as a possible reservoir and source of nutrients is less clear, especially in central Europe.MethodsBased on a chronosequence of known ages of logs, we analyzed the nutrients stored in CWD of Fagus sylvatica, Picea abies, and Pinus sylvestris at different sites in Germany. To quantify nutrient concentrations, we assessed the use of Near Infrared Reflectance Spectroscopy (NIRS) to determine the chemical properties of CWD.ResultsNIRS models were suitable to predict concentrations of C, N, P, lignin and extractives. Concentrations of most nutrients increased with mass loss, with the exception of potassium, which decreased for beech and pine and remained relatively constant for spruce. The highest nutrient concentrations (N, P, S, Ca and Mn, except Mg and K) were generally observed in highly decomposed spruce logs. The net effect of decreasing CWD mass and increasing nutrient concentrations was either a decreasing (N, P and K in beech; P, Mg, K and Mn in pine), constant (S, Ca and Mg in beech; N, S and Ca in pine) or increasing amount of nutrients (N, P, S and Ca in spruce; Mn in beech) in the logs over the course of decomposition. The C/N ratio decreased for all tree species, most markedly for spruce from ca. 1000 at the beginning of the decomposition process to 180 at 36 years. The N/P ratio converged to a value of about 30 for all three species. Lignin concentrations increased for spruce and beech and remained constant for pine.ConclusionsOur results indicate that most nutrients remain in CWD for long periods. Nutrients may be used and cycled by microorganisms within CWD, but with the exception of P (in beech), Mg (in pine) and K (in beech and pine), there appears to be little net nutrient export until two thirds of the mass is lost. Instead, N, P, S and Ca were accumulated in spruce logs, indicating that CWD became a net sink rather than a net source of some nutrients for several decades.
Highlights
Coarse woody debris (CWD) is very important for forest ecosystems, for biodiversity and carbon storage
Some studies have found that the store of nutrients in dead wood is significant when compared to other biomass pools in boreal forest ecosystems of northwestern Russia, whereas others have found no substantial contribution of CWD to the nutrient cycle for North-American coniferous forests (Laiho and Prescott 2004)
Near Infrared Reflectance Spectroscopy (NIRS) Our results demonstrate that concentrations of C, the nutrients N and P and the organic constituents lignin and extractives in dead wood can be predicted with NIRS
Summary
Coarse woody debris (CWD) is very important for forest ecosystems, for biodiversity and carbon storage. Coarse woody debris (CWD) is structurally and functionally very important for forest ecosystems, in particular in relation to biodiversity (Siitonen 2001; Grove et al 2002; Müller and Bütler 2010) and carbon sequestration (Harmon et al 1986; Turner et al 1995; Pregitzer and Euskirchen 2004). It can clearly play a key role in the carbon and nutrient cycle, i.e. as a temporary reservoir, but its importance varies with context. Accumulation of CWD on the forest floor can improve soil quality locally and provide hotspots for certain nutrients and the organisms that depend on them, such as the gastropod community that depend on Ca in CWD in forests on highly acidic soils (Kappes 2005; Kappes et al 2006, 2007)
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